Wireless communications system, base station, terminal, and processing method

ABSTRACT

A wireless communications system configured to use a predetermined bandwidth of a Unlicensed bandwidth, includes a base station; and one or more terminals connected to the base station. The one or more terminals calculate a transmission start timing according to a control signal from the base station, perform a process of detecting a wireless signal of the predetermined bandwidth before the transmission start timing, and when a state in which no wireless signal of the predetermined bandwidth is detected has elapsed for a predetermined period, the one or more terminals start transmission from the calculated transmission start timing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication PCT/JP2014/079511, filed on Nov. 6, 2014, and designatingthe U.S., the entire contents of which are incorporated herein byreference.

FIELD

The embodiments discussed herein relate to a wireless communicationssystem, a base station, a terminal, and a processing method.

BACKGROUND

Long Term Evolution (LTE) mobile communication, LTE-advanced mobilecommunication and the like are conventionally known. A technique ofperforming carrier aggregation (CA) using unlicensed spectrum is furtherknown (for example, refer to Published Japanese-Translation of PCTApplication, Publication No. 2014-500685)

SUMMARY

According to an aspect of an embodiment, a wireless communicationssystem configured to use a predetermined bandwidth of a Unlicensedbandwidth, includes a base station; and one or more terminals connectedto the base station. The one or more terminals calculate a transmissionstart timing according to a control signal from the base station,perform a process of detecting a wireless signal of the predeterminedbandwidth before the transmission start timing, and when a state inwhich no wireless signal of the predetermined bandwidth is detected haselapsed for a predetermined period, the one or more terminals starttransmission from the calculated transmission start timing.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a diagram depicting an example of a wireless communicationssystem according to an embodiment;

FIG. 1B is a diagram depicting an example of signal flow in the wirelesscommunications system depicted in FIG. 1A;

FIG. 2 is a diagram depicting an example of a bandwidth of an unlicensedbandwidth;

FIG. 3 is a diagram depicting an example of a timing of signaltransmission and reception, and carrier sensing;

FIG. 4 is a diagram depicting an example of notification of acell-shared offset by a base station;

FIG. 5A is a diagram depicting an example of a transmission start timingof terminals;

FIG. 5B is a diagram depicting a modification example of thetransmission start timing of the terminals;

FIG. 6 is a flowchart of an example of processing by the terminals;

FIG. 7A is a diagram depicting an example of the base station accordingto the embodiment;

FIG. 7B is a diagram depicting an example of signal flow in the basestation depicted in FIG. 7A;

FIG. 7C is a diagram depicting an example of hardware configuration ofthe base station;

FIG. 8A is a diagram depicting an example of the terminal according tothe embodiment;

FIG. 8B is a diagram depicting an example of signal flow in the terminaldepicted in FIG. 8A;

FIG. 8C is a diagram depicting an example of hardware configuration ofthe terminal;

FIG. 9A is a diagram depicting an example of the base station accordingto a modification example;

FIG. 9B is a diagram depicting an example of signal flow at the basestation depicted in FIG. 9A; and

FIG. 10 is a diagram depicting an example of signal flow in the terminalaccording to the modification example.

DESCRIPTION OF THE INVENTION

An embodiment of a wireless communications system, a base station, aterminal, and a processing method according to the present inventionwill be described in detail with reference to the accompanying drawings.

FIG. 1A is a diagram depicting an example of the wireless communicationssystem according to the embodiment. FIG. 1B is a diagram depicting anexample of signal flow in the wireless communications system depicted inFIG. 1A. As depicted in FIGS. 1A and 1B, a wireless communicationssystem 100 according to the embodiment includes a base station 110 andterminals 120, 130.

The wireless communications system 100 is a system that shares apredetermined bandwidth with other wireless communications systems. Thepredetermined bandwidth is a bandwidth shared by multiple wirelesscommunications systems including the wireless communications system 100.An example of the predetermined bandwidth is an unlicensed bandwidth(non-licensed bandwidth). An example of an unlicensed bandwidth is anIndustry-Science-Medical (ISM) bandwidth (2.4 [GHz] bandwidth), a 5[GHz] bandwidth, etc. used in a wireless local area network (WLAN), orthe like.

The base station 110 uses the predetermined bandwidth shared with otherwireless communications systems to wirelessly communicate with theterminals 120, 130 connected to the base station 110 (connectedthereto). Further, the base station 110, for example, may wirelesslycommunicate with the terminals 120, 130 by carrier aggregation, via abandwidth used exclusively by the wireless communications system 100(the system thereof) and the predetermined bandwidth shared with otherwireless communications systems.

In the wireless communications system 100, for example, uplink usermultiplexing is performed where the terminals 120, 130 concurrentlytransmit wireless signals to the base station 110 by the predeterminedbandwidth. At this time, the terminals 120, 130 transmit the wirelesssignals to the base station 110 by differing bandwidths among bandwidthsincluded in the predetermined bandwidth. Further, for example, whenMulti User Multiple Input Multiple Output (multiuser MIMO) is used, theterminals 120, 130 transmit the wireless signals to the base station 110by the same bandwidth.

The base station 110 includes a control unit 111 and a receiving unit112. The control unit 111 transmits to the terminals 120, 130, aparameter for calculating a predetermined timing common between theterminals 120, 130. The receiving unit 112 receives wireless signalstransmitted by the terminals 120, 130. For example, the receiving unit112 receives data signals that are addressed to the base station 110 andincluded in the wireless signals transmitted by the terminals 120, 130.

The terminal 120 includes a detecting unit 121 and a transmitting unit122. Here, although configuration of the terminal 120 is described, theconfiguration of the terminal 130 is identical to that of the terminal120. The detecting unit 121 starts, at the predetermined timing commonbetween the terminals 120, 130, a process of detecting a wireless signalof the predetermined bandwidth. As a result, the timing at which theterminals 120, 130 start the process of detecting a wireless signal ofthe predetermined bandwidth may be made to coincide. The predeterminedtiming, for example, may be calculated based on the parametertransmitted to the terminals 120, 130 by the base station 110. Thedetecting unit 121 notifies the transmitting unit 122 of the detectionresult.

Based on the detection result from the detecting unit 121, thetransmitting unit 122, at a timing when a state in which no wirelesssignal of the predetermined bandwidth is detected has continued for apredetermined period, starts transmitting a wireless signal of abandwidth corresponding to the terminal 120, among the bandwidthsincluded in the predetermined bandwidth. The predetermined period is aperiod shared between the terminals 120, 130. As a result, the timing atwhich the terminals 120, 130 transmit a wireless signal may be made tocoincide.

According to the configuration depicted in FIGS. 1A and 1B, thepredetermined timing at which the terminals 120, 130 start detection foravailable bandwidth that is shared with other wireless communicationssystems, and the predetermined period until a wireless signal istransmitted by the terminals 120, 130 may be made to coincide. As aresult, the timing of wireless signal transmission at the terminals 120,130 may be made to coincide and transmission collisions between theterminals 120, 130 in the shared bandwidth may be avoided. Thus, uplinkfrequency-division user multiplexing in the shared bandwidth orspatial-division user multiplexing by multiuser MIMO becomes possible,enabling throughput to be improved.

Wireless signal detection in the predetermined bandwidth by thedetecting unit 121 is, for example, Clear Channel Assessment (CCA) ofdetecting carrier availability in the predetermined bandwidth, forexample, carrier sensing.

For example, wireless signal detection in the predetermined bandwidth isa process of detecting the reception power (reception energy) of a radiowave in the predetermined bandwidth and comparing the detected receptionpower and a predetermined power to detect a wireless signal.Alternatively, wireless signal detection in the predetermined bandwidthmay be a process of detecting wireless signals by detecting apredetermined pattern (e.g., preamble) of a wireless signal, based on aradio wave in the predetermined bandwidth.

Further, the process of detecting a wireless signal of the predeterminedbandwidth is, for example, a process of detecting a wireless signal inthe entire predetermined bandwidth. Alternatively, the process ofdetecting a wireless signal of the predetermined bandwidth may beprocess of detecting a wireless signal in only the bandwidth in whichthe terminal transmits wireless signals, among those of thepredetermined bandwidth.

Although a configuration in which the terminals 120, 130 calculate thepredetermined timing based on a parameter transmitted from the basestation 110 is explained, the base station 110 does not have to transmitthe parameter. In this case, the terminals 120, 130, for example, maycalculate the predetermined timing based on information shared betweenthe terminals 120, 130. Further, in this case, the base station 110 mayomit the control unit 111.

The information shared between the terminals 120, 130, for example, maybe information that includes cell identification information (e.g., cellID) of the base station 110. Further, the information shared by theterminals 120, 130 may be information that includes identificationinformation (e.g., subframe number) of a subframe for performing theprocess of detecting a wireless signal.

FIG. 2 is a diagram depicting an example of a bandwidth of theunlicensed bandwidth. In the wireless communications system 100, forexample, an unlicensed bandwidth 200 is used. In the example depicted inFIG. 2, the unlicensed bandwidth 200 is a bandwidth of 20 [MHz].

The unlicensed bandwidth 200 is a bandwidth shared between the wirelesscommunications system 100 and other systems. Other systems are, forexample, WLAN wireless communications systems, LTE or LTE-A wirelesscommunications systems different from the wireless communications system100, etc.

The unlicensed bandwidth 200 includes sub-bands #1, #2. Here,description will be given concerning a case where the base station 110has assigned the sub-band #1 to uplink transmission of the terminal 120and the sub-band #2 to uplink transmission of the terminal 130.

FIG. 3 is a diagram depicting an example of the timing of signaltransmission and reception, and carrier sensing. In FIG. 3, a horizontalaxis (t) represents time.

A reference timing 301 is a common reference timing in a cell of thebase station 110. In the example depicted in FIG. 3, the referencetiming 301 is a timing at which the base station 110 transmits andreceives signals by the sub-bands #1, #2. However, the reference timing301 may be a timing different from the timing at which the base station110 transmits and receives signals by the sub-bands #1, #2.

A cell-shared offset 302 is a common offset in a cell of the basestation 110 and is a parameter for calculating the reference timing 301(predetermined timing). In the example depicted in FIG. 3, thecell-shared offset 302 is an offset between the reference timing 301 anda carrier sensing start timing 303.

The carrier sensing start timing 303 is a timing at which the terminals120, 130 start carrier sensing. Further, the carrier sensing starttiming 303 is a timing uniquely determined from the reference timing 301and the cell-shared offset 302.

In the example depicted in FIG. 3, the carrier sensing start timing 303is a timing preceding the reference timing 301 by the cell-shared offset302. However, the carrier sensing start timing 303, for example, may bea timing after the reference timing 301 by the cell-shared offset 302.

A specified idle period 304 is a standard period for determiningbandwidth availability. For example, when the terminals 120, 130 performcarrier sensing and an idle state (I) has continued during the specifiedidle period 304, it is determined that bandwidth is available.

A planned transmission-start-timing 305 is a timing at which theterminals 120, 130 are to start transmitting wireless signals, whendetermining, by carrier sensing, that bandwidth is available. Forexample, the planned transmission-start-timing 305 is a timing after thecarrier sensing start timing 303 by the specified idle period 304.

In the example depicted in FIG. 3, the terminal 120 starts carriersensing at the carrier sensing start timing 303 and since an idle state(I) has continued for the specified idle period 304, the terminal 120starts transmitting a wireless signal at the plannedtransmission-start-timing 305. At this time, the terminal 120 firsttransmits a dummy signal 311 and thereafter, transmits a data signal312.

Similarly, the terminal 130 also starts carrier sensing at the carriersensing start timing 303 and since an idle state (I) has continued forthe specified idle period 304, the terminal 130 starts transmitting awireless signal at the planned transmission-start-timing 305. At thistime, the terminal 130 first transmits a dummy signal 321 andthereafter, transmits a data signal 322.

As a result, a reception timing of the data signals 312, 322 at the basestation 110 may be made to coincide with the reference timing 301.Further, from the planned transmission-start-timing 305 until the startof transmission of the data signals 312, 322, transmission of a wirelesssignal (interruption) by another communications apparatus may beprevented. Another communications apparatus is, for example, acommunications apparatus of a wireless communications system differentfrom the wireless communications system 100.

In the example depicted in FIG. 3, although a case has been described inwhich the terminals 120, 130 transmit the dummy signals 311, 321,respectively, the terminals 120, 130 may transmit a preamble in place ofthe dummy signals 311, 321. The preambles transmitted by the terminals120, 130 are wireless signals of a predetermined pattern and, forexample, are preambles of the data signals 312, 322.

Further, in the example depicted in FIG. 3, a case has been described inwhich the cell-shared offset 302 is an offset between the referencetiming 301 and the carrier sensing start timing 303. However, withoutlimitation hereto, the cell-shared offset 302, for example, may be anoffset between the reference timing 301 and the plannedtransmission-start-timing 305.

In this case, the terminals 120, 130 calculate, as the plannedtransmission-start-timing 305, a timing that precedes the referencetiming 301 by the cell-shared offset 302. The terminals 120, 130calculate, as the carrier sensing start timing 303, a timing thatprecedes the calculated planned transmission-start-timing 305 by thespecified idle period 304, and start carrier sensing.

Further, the cell-shared offset 302, for example, may be of a lengththat differs for each predetermined interval (e.g., for each subframe,for every several subframes, etc.). As a result, for example, anoccurrence of continuous collisions consequent to the terminals 120, 130transmitting wireless signals at the same timing as a communicationsapparatus of a neighbor cell may be avoided.

Further, the cell-shared offset 302 may be an offset determined based ona value unique to a cell of the base station 110 (e.g., cell number). Asa result, collisions with a communications apparatus of a neighbor cellmay be suppressed.

For example, the base station 110 may determine the cell-shared offset302 based on at least one of the subframe number and the cell number.For instance, the base station 110 determines the cell-shared offset 302based on equation (1).offset=u+((Σ_(i=0) ⁷ c(8v+i)·2^(i))mod L+w)mod L  (1)

c(i): pseudorandom number sequence

In equation (1), offset is the cell-shared offset 302 that is to bedetermined; c(i) is a pseudorandom number sequence; and u, v, w, and Lare constants predefined in the wireless communications system 100. Forc(i), for example, the Gold sequence specified in TS36.211 of the 3GPPmay be used. For example, for c(i), equation (2) may be used.c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  (2)

(where, N_(c)=1600)

In equation (2) x₁ (n), x₂ (n) are each a sequence called an m-sequence,and the initial value is obtained by equation (3).x ₁(0)=1,x ₁(n)=0,n=1,2 . . . ,30c _(init)=Σ_(i=0) ³⁰ x ₂(f)·2^(i)  (3)

For example, the base station 110 may substitute a subframe number forat least one of v, w, and c_(init) and thereby, determine thecell-shared offset 302 that is based on the subframe number.Alternatively, the base station 110 may substitute a cell number for atleast one of v, w, and c_(init) and thereby, determine the cell-sharedoffset 302 that is based on the cell number.

Alternatively, the base station 110 may substitute a subframe number anda cell number for at least one of v, w, c_(init) and thereby, determinethe cell-shared offset 302 that is based on the subframe number and thecell number. For example, in equations (1) to (3), the base station 110substitutes a subframe number for v and substitutes a cell number forc_(init), and is able to determine w=0, L=64, u=12 as the cell-sharedoffset 302.

Further, the cell-shared offset 302 may be an offset that is determinedbased on a random number. As a result, for example, the occurrence ofcontinuous collisions consequent to the terminals 120, 130 transmittingwireless signals at the same timing as a communications apparatus of aneighbor cell may be avoided. For example, the base station 110 maydetermine the cell-shared offset 302 by equation (4).cell-shared offset=a×unit time  (4)

In equation (4), “a” is a random number randomly selected from {0, 1, .. . A}. “A” is a value less than the subframe length in the wirelesscommunications system 100.

FIG. 4 is a diagram depicting an example of notification of thecell-shared offset by the base station. As depicted in FIG. 4, forexample, the base station 110 notifies the terminals 120, 130 connectedto a cell thereof of the cell-shared offset. For example, a commondownlink control channel such as a Physical Downlink Control Channel(PDCCH) or the like may be used for the notification of the cell-sharedoffset.

Further, for example, upper layer control information such as radioresource control (RRC) or the like may be used for the notification ofthe cell-shared offset. Further, for example, a broadcast channel suchas a Physical Broadcast Channel (PBCH) may be used for the notificationof the cell-shared offset.

Further, the base station 110 may notify the terminals 120, 130 of aparameter that enables calculation of the cell-shared offset at theterminals 120, 130 and may thereby indirectly notify the terminals 120,130 of the cell-shared offset. In this case, the terminals 120, 130calculate the cell-shared offset based on the parameter notified by thebase station 110.

FIG. 5A is a diagram depicting an example of a transmission start timingof terminals. In FIG. 5A, portions identical to those depicted in FIG. 3are given the same reference numerals used in FIG. 3 and descriptionthereof is omitted hereinafter. Subframe borders 511, 512 are borders ofsubframes in downlink reception from the base station 110 to theterminal 120. Subframe borders 521, 522 are borders of subframes indownlink reception from the base station 110 to the terminal 130.

For example, the base station 110 transmits downlink signals to theterminals 120, 130 at the same timing (the reference timing 301). On thecontrary, consequent to a difference in a propagation delay T1 betweenthe base station 110 and the terminal 120, and a propagation delay T2between the base station 110 and the terminal 130, the subframe borders511, 512 and the subframe borders 521, 522 have different timings.

For example, the subframe border 512 is a timing after the referencetiming 301 by the propagation delay T1. A data-signal transmission starttiming 531 is a timing at which the terminal 120 starts transmitting thedata signal 312 and is a timing preceding the reference timing 301 bythe propagation delay T1.

The terminal 120 is capable of identifying, as the data-signaltransmission start timing 531, a timing preceding the subframe border512 by the propagation delay T1×2. The terminal 120 starts transmittingthe data signal 312 at the data-signal transmission start timing 531whereby the reception timing of the data signal 312 at the base station110 may be made to coincide with the reference timing 301.

Further, the subframe border 522 is a timing after the reference timing301 by the propagation delay T2. A data-signal transmission start timing532 is a timing at which the terminal 130 starts transmitting the datasignal 322 and is a timing preceding the reference timing 301 by thepropagation delay T2. The terminal 130 is capable of identifying, as thedata-signal transmission start timing 532, a timing preceding thesubframe border 522 by the propagation delay T2×2. The terminal 130starts transmitting the data signal 322 at the data-signal transmissionstart timing 532 whereby the reception timing of the data signal 322 atthe base station 110 may be made to coincide with the reference timing301.

Further, the terminal 120 is able to identify the propagation delay T1×2based on a timing advance (TA) received from the base station 110. Forexample, the base station 110 measures the propagation delay T1 betweenthe base station 110 and the terminal 120, and transmits to the terminal120, a timing advance indicating a value that is two times the measuredpropagation delay T1. With this, the terminal 120 is able to identify,as the propagation delay T1×2, the value of the timing advance receivedfrom the base station 110.

Further, the terminal 130 is able to identify the propagation delay T2×2based on the timing advance received from the base station 110. Forexample, the base station 110 measures the propagation delay T2 betweenthe base station 110 and the terminal 130, and transmits to the terminal130, a timing advance indicating a value that is two times the measuredpropagation delay T2. With this, the terminal 130 is able to identify asthe propagation delay T2×2, the value of the timing advance receivedfrom the base station 110.

Further, the interval during which the terminal 120 transmits the dummysignal 311, for example, may be an interval from the plannedtransmission-start-timing 305 until the data-signal transmission starttiming 531. Further, the interval during which the terminal 130transmits the dummy signal 321, for example, may be an interval from theplanned transmission-start-timing 305 until the data-signal transmissionstart timing 532.

FIG. 5B is a diagram depicting a modification example of thetransmission start timing of the terminals. In FIG. 5B, portionsidentical to those depicted in FIG. 5A are given the same referencenumeral used n FIG. 5A and description thereof will be omittedhereinafter. In FIG. 5B, a case in which multiuser MIMO is used isdescribed. In this case, the terminals 120, 130 are able to use the samebandwidth among the unlicensed bandwidth 200.

For example, description will be given concerning a case where the basestation 110 has assigned the sub-band #1 to the uplink transmission ofthe terminal 120 and has further assigned the sub-band #1 to the uplinktransmission of the terminal 130. In this case, as depicted in FIG. 5B,the terminal 130 performs carrier sensing in the sub-band #1 andtransmission of the dummy signal 321 and the data signal 322. The basestation 110 performs, in the sub-band #1, reception of the dummy signal321 and the data signal 322 from the terminal 130.

FIG. 6 is a flowchart of an example of processing by the terminals.Here, although processing by the terminal 120 will be described,processing by the terminal 130 is identical. The terminal 120 executesthe steps depicted in FIG. 6, when transmitting an uplink data signal,for example.

First, the terminal 120 calculates the carrier sensing start timingbased on the cell-shared offset (step S601). The terminal 120 stands byuntil the carrier sensing start timing calculated at step S601 (stepS602).

Next, the terminal 120 initializes m (m=0) (step S603). “m” is a countvalue for counting the number of executions of carrier sensing per unittime. Next, the terminal 120 determines whether m equals M-N (stepS604). “M” is the cell-shared offset and “N” is the specified idleperiod. Furthermore, the units of M and N are also the unit time of thecarrier sensing.

At step S604, when m is equal to M-N (step S604: YES), the terminal 120is able to determine that data signal transmission cannot be starteduntil the next reference timing 301 of the base station 110, even whenchannel availability has been detected by carrier sensing. In this case,the terminal 120 ends the series of operations.

At step S604, when m is not equal to M-N (step S604: NO), the terminal120 initializes n (n=0) (step S605). “n” is a count value for countingthe number of times that an idle state of the channel (bandwidth) isconsecutively detected by carrier sensing.

Next, the terminal 120 executes carrier sensing for the unit time (stepS606). Further, the terminal 120 increments m (m=m+1). Next, theterminal 120 determines based on the result of carrier sensing at stepS606, whether a channel is in an idle state (step S607). At step S607,the channel subject to idle state determination, for example, may beonly the sub-band (the sub-band #1) assigned to the terminal 120 or maybe the unlicensed bandwidth 200 entirely.

At step S607, if the channel is not in an idle state (step S607: NO),the terminal 120 returns to step S604. If the channel is in an idlestate (step S607: YES), the terminal 120 increments n (n=n+1) (stepS608).

Next, the terminal 120 determines whether n is equal to N (step S609).If n is not equal to N (step S609: NO), the terminal 120 returns to stepS606. If n is equal to N (step S609: YES), the terminal 120 transmits asignal by the uplink (step S610), ending the series of operations. Atstep S610, for example, as depicted in FIG. 3, the terminal 120 firsttransmits a dummy signal and thereafter, transmits a data signal.

In the example depicted in FIG. 6, although a process of calculating thecarrier sensing start timing when the terminal 120 transmits a signalhas been described, the terminal 120 may calculate the carrier sensingstart timing in advance based on the cell-shared offset.

FIG. 7A is a diagram depicting an example of the base station accordingto the embodiment. FIG. 7B is a diagram depicting an example of signalflow in the base station depicted in FIG. 7A. As depicted in FIGS. 7Aand 7B, the base station 110 has an antenna 701, a RF unit 702, anuplink baseband signal processing unit 703, a propagation delaymeasuring unit 704, an uplink transmission timing control unit 705, anda downlink baseband signal generating unit 706.

The antenna 701 receives signals wirelessly transmitted from theterminals 120, 130 and outputs the signals to the RF unit 702. Theantenna 701 further wirelessly transmits to the terminals 120, 130,signals output from the RF unit 702. The antenna 701 is not limited to asingle antenna and may be multiple antennas. For example, when multiuserMIMO is performed, the antenna 701 may be multiple antennas supportingmultiuser MIMO.

The RF unit 702 performs a RF reception process for uplink signalsoutput from the antenna 701. The RF reception process by the RF unit702, for example, includes amplification, frequency conversion from aradio frequency (RF) to a baseband, conversion from an analog signal toa digital signal, and the like. The RF unit 702 outputs to the uplinkbaseband signal processing unit 703, the signals subjected to the RFreception process.

Further, the RF unit 702 performs a RF transmission process for downlinksignals output from the downlink baseband signal generating unit 706.The RF transmission process by the RF unit 702, for example, includesconversion from a digital signal to an analog signal, frequencyconversion from a baseband to an RF band, amplification, and the like.The RF unit 702 outputs to the antenna 701, the signals subjected to theRF transmission process.

The uplink baseband signal processing unit 703 performs a basebandsignal process for uplink signals output from the RF unit 702. Theuplink baseband signal processing unit 703 outputs to the propagationdelay measuring unit 704, measurement-use signals included in dataobtained by the baseband signal process. The measurement-use signaloutput from the uplink baseband signal processing unit 703 to thepropagation delay measuring unit 704, for example, includes an uplinkreference signal (RS), a Random Access Channel (RACH) preamble, etc.from the terminals 120, 130.

The propagation delay measuring unit 704 measures the propagation delaysbetween the base station 110 and the terminals 120, 130, based on themeasurement-use signal output from the uplink baseband signal processingunit 703. For example, the propagation delay measuring unit 704 measuresthe propagation delay between the base station 110 and the terminal 120,based on the RS, the RACH preamble, etc. transmitted from the terminal120. Further, the propagation delay measuring unit 704 measures thepropagation delay between the base station 110 and the terminal 130,based on the RS, RACH preamble, etc. output from the terminal 130.

The propagation delay measuring unit 704, with respect to each of theterminals 120, 130, outputs to the downlink baseband signal generatingunit 706, a timing advance that is based on the measured propagationdelay values. The timing advance, for example, is information indicatinga value that is two times the measured propagation delay.

The uplink transmission timing control unit 705 controls thetransmission timing of uplinks from the terminals 120, 130 to the basestation 110. For example, the uplink transmission timing control unit705 determines the cell-shared offset between the carrier sensing starttiming and the reference timing and notifies the downlink basebandsignal generating unit 706 of the determined cell-shared offset. Thecell-shared offset determined by the uplink transmission timing controlunit 705, for example, is the cell-shared offset 302 depicted in FIG. 3.

The downlink baseband signal generating unit 706 generates downlinkbaseband signals from the base station 110 to the terminals 120, 130.The signals generated by the downlink baseband signal generating unit706 include the timing advance output from the propagation delaymeasuring unit 704 and the cell-shared offset notified by the uplinktransmission timing control unit 705. The downlink baseband signalgenerating unit 706 outputs the generated signal to the RF unit 702.

The control unit 111 depicted in FIGS. 1A and 1B, for example, may berealized by the antenna 701, the RF unit 702, the uplink transmissiontiming control unit 705, and the downlink baseband signal generatingunit 706. The receiving unit 112 depicted in FIGS. 1A and 1B, forexample, may be realized by the antenna 701, the RF unit 702, and theuplink baseband signal processing unit 703.

FIG. 7C is a diagram depicting an example of hardware configuration ofthe base station. The base station 110 depicted in FIGS. 7A and 7B, forexample, may be realized by a communications apparatus 730 depicted inFIG. 7C. The communications apparatus 730 includes a processor 731, amain memory apparatus 732, and an auxiliary memory apparatus 733, anetwork interface 734, a transceiver 735, and an antenna 736. Theprocessor 731, the main memory apparatus 732, the auxiliary memoryapparatus 733, the network interface 734, and the transceiver 735 areconnected by a bus 739.

The processor 731 governs overall control of the communicationsapparatus 730. The processor 731, for example, may be realized by acentral processing unit (CPU). The main memory apparatus 732, forexample, is used as a work area of the processor 731. The main memoryapparatus 732, for example, may be realized by random access memory(RAM).

The auxiliary memory apparatus 733, for example, may be non-volatilememory such as a magnetic disk, an optical disk, flash memory, and thelike. The auxiliary memory apparatus 733 stores various programs thatcause the communications apparatus 730 to operate. The programs storedby the auxiliary memory apparatus 733 are loaded onto the main memoryapparatus 732 and are executed by the processor 731.

The network interface 734, for example, is a communications interfacethat performs wireless or wired communication with external devices ofthe communications apparatus 730 (e.g., core network, higher device ofthe base station 110, etc.). The network interface 734 is controlled bythe processor 731.

The transceiver 735 is a communications interface that uses the antenna736 and performs wireless communication with other communicationsapparatuses (e.g., the terminals 120, 130). The transceiver 735 iscontrolled by the processor 731.

The antenna 701 depicted in FIGS. 7A and 7B, for example, may berealized by the antenna 736. The RF unit 702 depicted in FIGS. 7A and7B, for example, may be realized by the transceiver 735.

The uplink baseband signal processing unit 703, the propagation delaymeasuring unit 704, the uplink transmission timing control unit 705, andthe downlink baseband signal generating unit 706 depicted in FIGS. 7Aand 7B, for example, may be realized by the processor 731.

FIG. 8A is a diagram depicting an example of the terminal according tothe embodiment. FIG. 8B is a diagram depicting an example of signal flowin the terminal depicted in FIG. 8A. In FIGS. 8A and 8B, althoughconfiguration of the terminal 120 will be described, the configurationof the terminal 130 is identical.

As depicted in FIGS. 8A and 8B, the terminal 120 includes an antenna801, a RF unit 802, a downlink baseband signal processing unit 803, anuplink transmission timing control unit 804, and an uplink basebandsignal generating unit 805.

The antenna 801 receives signals wirelessly transmitted from the basestation 110 and outputs the signals to the RF unit 802. The antenna 801further wirelessly transmits to the base station 110, signals outputfrom the RF unit 802.

The RF unit 802 performs a RF reception process for uplink signalsoutput from the antenna 801. The RF reception process by the RF unit 802includes, for example, amplification, frequency conversion from a RFband to a baseband, conversion from an analog signal to a digitalsignal, and the like. The RF unit 802 outputs to the downlink basebandsignal processing unit 803, the signals subjected to the RF receptionprocess.

Further, the RF unit 802 performs a RF transmission process for uplinksignals output from the uplink baseband signal generating unit 805. TheRF transmission process by the RF unit 802 includes, for example,conversion from a digital signal to an analog signal, frequencyconversion from a baseband to a RF band, amplification, and the like.The RF unit 802 outputs to the antenna 801, the signal subject to the RFtransmission process.

The downlink baseband signal processing unit 803 performs a basebandsignal process for downlink signals output from the RF unit 802. Thedownlink baseband signal processing unit 803 outputs to the uplinktransmission timing control unit 804, control information obtained bythe baseband signal process.

The control information output from the downlink baseband signalprocessing unit 803 to the uplink transmission timing control unit 804includes, for example, information such as a downlink reception timing,a timing advance from the base station 110, a cell-shared offset fromthe base station 110, and the like. The downlink reception timing, forexample, is the timing of subframe borders 511, 512 depicted in FIG. 5A.The timing advance, for example, is information indicating a value thatis two times the propagation delay T1 depicted in FIG. 5A. Thecell-shared offset, for example, is the cell-shared offset 302 depictedin FIGS. 3 and 5A.

The uplink transmission timing control unit 804 determines a carriersensing start timing and an uplink transmission start timing, based onthe control information output from the downlink baseband signalprocessing unit 803.

The carrier sensing start timing determined by the uplink transmissiontiming control unit 804, for example, is the carrier sensing starttiming 303 depicted in FIG. 5A. For example, the uplink transmissiontiming control unit 804 determines the carrier sensing start timingbased on the cell-shared offset, the propagation delay indicated by thetiming advance, and a subframe border that is based on a downlinkreception timing. The uplink transmission timing control unit 804notifies the uplink baseband signal generating unit 805 of thedetermined carrier sensing start timing.

A transmission start timing determined by the uplink transmission timingcontrol unit 804, for example, is the data-signal transmission starttiming 531 depicted in FIG. 5A. For example, the uplink transmissiontiming control unit 804 determines the data-signal transmission starttiming, based on the propagation delay indicated by the timing advanceand a subframe border that is based on the downlink reception timing.The uplink transmission timing control unit 804 notifies the uplinkbaseband signal generating unit 805 of the determined data-signaltransmission start timing.

The uplink baseband signal generating unit 805 performs carrier sensingcontrol and uplink baseband signal generation, based on the timingsnotified by the uplink transmission timing control unit 804. The uplinkbaseband signal generating unit 805 outputs the generated signals to theRF unit 802.

For example, the uplink baseband signal generating unit 805 controls theRF unit 802 to perform carrier sensing at the carrier sensing starttiming notified by the uplink transmission timing control unit 804. Theuplink baseband signal generating unit 805 starts wireless signaltransmission, when, as a result of carrier sensing, idle state for thespecified idle period (the specified idle period 304 depicted in FIG.5A) is detected.

For example, the uplink baseband signal generating unit 805 firsttransmits a dummy signal (the dummy signal 311 depicted in FIG. 5A). Theuplink baseband signal generating unit 805 transmits a data signal (thedata signal 312 depicted in FIG. 5A) at the data-signal transmissionstart timing notified by the uplink transmission timing control unit804.

The detecting unit 121 and the transmitting unit 122 depicted in FIGS.1A and 1B, for example, may be realized by the antenna 801, the RF unit802, the uplink transmission timing control unit 804, and the uplinkbaseband signal generating unit 805.

FIG. 8C is a diagram depicting an example of hardware configuration ofthe terminal. The terminal 120 depicted in FIGS. 8A and 8B, for example,may be realized by a communications apparatus 830 depicted in FIG. 8C.The communications apparatus 830 includes a processor 831, a main memoryapparatus 832, an auxiliary memory apparatus 833, a user interface 834,a transceiver 835, and an antenna 836. The processor 831, the mainmemory apparatus 832, the auxiliary memory apparatus 833, the userinterface 834, and the transceiver 835 are connected by a bus 839.

The processor 831 governs overall control of the communicationsapparatus 830. The processor 831, for example, may be realized by a CPU.The main memory apparatus 832, for example, is used as a work area ofthe processor 831. The main memory apparatus 832, for example, may berealized by RAM.

The auxiliary memory apparatus 833, for example, is non-volatile memorysuch as a magnetic disk, an optical disk, flash memory, and the like.The auxiliary memory apparatus 833 stores various programs that causethe communications apparatus 830 to operate. The programs stored by theauxiliary memory apparatus 833 are loaded onto the main memory apparatus832 and are executed by the processor 831.

The user interface 834, for example, may include an input device thatreceives operational input from a user, an output device that outputsinformation to the user. The input device may be realized by, forexample, a key (e.g., a keyboard), a remote controller, or the like. Theoutput device may be realized by, for example, a display, a speaker, orthe like. Further, the input device and the output device may berealized by a touch panel or the like. The user interface 834 iscontrolled by the processor 831.

The transceiver 835 is a communications interface that uses the antenna836 and performs wireless communication with other communicationsapparatuses (e.g., the base station 110). The transceiver 835 iscontrolled by the processor 831.

The antenna 801 depicted in FIGS. 8A and 8B may be realized by, forexample, the antenna 836. The RF unit 802 depicted in FIGS. 8A and 8Bmay be realized by, for example, the transceiver 835. The downlinkbaseband signal processing unit 803, the uplink transmission timingcontrol unit 804, and the uplink baseband signal generating unit 805depicted in FIGS. 8A and 8B may be realized by, for example, theprocessor 831.

Although a configuration in which the base station 110 notifies theterminals 120, 130 of the cell-shared offset has been described,configuration may be such that the base station 110 does not notify theterminals 120, 130 of the cell-shared offset. In this case, theterminals 120, 130, for example, use a recognized parameter commonwithin the cell of the base station 110 to calculate the cell-sharedoffset. As a result, even without the base station 110 notifying theterminals 120, 130 of the cell-shared offset, the terminals 120, 130 maycalculate the cell-shared offset.

FIG. 9A is a diagram depicting an example of the base station accordingto a modification example. FIG. 9B is a diagram depicting an example ofsignal flow at the base station depicted in FIG. 9A. In FIGS. 9A and 9B,portions identical to those depicted in FIGS. 7A and 7B are given thesame reference numerals used in FIGS. 7A and 7B and description thereofis omitted hereinafter. As depicted in FIGS. 9A and 9B, the base station110 according to the modification example may be configured to omit theuplink transmission timing control unit 705 in the configurationdepicted in FIGS. 7A and 7B.

FIG. 10 is a diagram depicting an example of signal flow in the terminalaccording to the modification example. In FIG. 10, portions identical tothose depicted in FIGS. 8A and 8B are given the same reference numeralsused in FIGS. 8A and 8B and description thereof is omitted hereinafter.Configuration of the terminal 120 according to the modification exampleis the same as the configuration of the terminal 120 depicted in FIG.8A. However, as depicted in FIG. 10, in the terminal 120 according tothe modification example, the cell-shared offset is not included in thecontrol information output from the downlink baseband signal processingunit 803 to the uplink transmission timing control unit 804.

The uplink transmission timing control unit 804, for example, calculatesthe cell-shared offset based on at least one of the subframe number andthe cell number. As a result, the terminals 120, 130 calculate thecell-shared offset, enabling the transmission timings of the wirelesssignals by the terminals 120, 130 to be made to coincide.

As described, according to the wireless communications system, the basestation, the terminal, and the processing method, uplink usermultiplexing in a shared bandwidth becomes possible and throughput maybe improved.

For example, conventionally, under LTE, to cope with traffic increases,data offloading from an exclusive bandwidth (licensed bandwidth) using anon-licensed bandwidth has been proposed. A non-licensed bandwidth, forexample, is called an unlicensed bandwidth or a common-use bandwidth(shared bandwidth).

For example, a Licensed-Assisted Carrier Aggregation scheme oftransmitting control information such as a response signal (ACK/NACK) byan exclusive bandwidth and transmitting data by an unlicensed bandwidthis under investigation.

In an unlicensed bandwidth, in addition to coexistence between LTE-usystems, coexistence with other wireless systems such as that of a WLANis necessary. Under radio laws of Japan and Europe, before thetransmission of a wireless signal, it has to be confirmed by carriersensing that a channel is not being used by another wireless system (isin an idle state).

In practice, in an unlicensed bandwidth, in a WLAN, time-division usermultiplexing is performed in which a single user (station) uses theentire bandwidth. In contrast, under LTE practically implemented in alicensed bandwidth, user multiplexing is not only performed by timedivision but also by frequency division. Furthermore, spatial-divisionuser multiplexing by MIMO may be performed.

In other words, under LTE, although user multiplexing is performed inthe same bandwidth, a method related to realizing uplink transmission inan unlicensed bandwidth has not been established. For example, a casewhere random backoff (Random Backoff) is performed according to terminalafter confirming non-usage (idle state) for a specified idle period likea WLAN will be described. In this case, a terminal for which the backoffinterval is long may detect by carrier sensing, a wireless signal from aterminal for which the backoff interval is short and may become unableto transmit a wireless signal.

For example, when a terminal performs carrier sensing for the entireunlicensed bandwidth (for example, a 20 [MHz] width), detectionincluding sub-bands other than the planned sub-band for the terminal toperform transmission is performed. Therefore, consequent to wirelesssignals transmitted by other terminals on other sub-bands, the channelis likely to be determined to be busy and the terminal may become unableto transmit a wireless signal.

Even in a case where carrier sensing is performed only in the plannedsub-band for wireless signal transmission by the terminal, the channelmay be determined to be in a busy state consequent to leaked power froma wireless signal transmitted by a terminal on an adjacent sub-band.Therefore, a situation in which wireless signal transmission cannot beperformed may occur.

Further, when multiuser MIMO is used, since spatial multiplexing on thesame bandwidth is performed, the channel may be determined to be busyconsequent to a signal of a multiplexing counterpart terminal, resultingin a situation in which wireless signal transmission cannot beperformed.

In contrast, according to the embodiment, for example, the uplinktransmission start time for terminals in the same cell may be made to bethe same. For example, the carrier sensing start timing and thetransmission start timing for wireless signals are determined based on ashared offset from a reference timing of each cell, enabling the uplinktransmission start times to be made the same.

As a result, in an unlicensed bandwidth, carrier sensing according toterminal is performed and the wireless signal transmission timing at theterminals may be made to be the same. Therefore, uplink usermultiplexing in a single cell becomes possible, enabling throughput tobe improved.

However, in a system that uses a shared bandwidth such as an unlicensedbandwidth, for example, the need to confirm the bandwidth beforetransmitting signals and the temporal overlap of wireless signaltransmission by multiple terminals were not anticipated. Therefore, usermultiplexing by frequency-division is difficult and uplink throughputmay not be improved by user multiplexing.

According to one aspect of the present invention, an effect is achievedin that uplink user multiplexing in a shared bandwidth is enabled andthroughput can be improved.

All examples and conditional language provided herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventor to further the art, and arenot to be construed as limitations to such specifically recited examplesand conditions, nor does the organization of such examples in thespecification relate to a showing of the superiority and inferiority ofthe invention. Although one or more embodiments of the present inventionhave been described in detail, it should be understood that the variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention.

In relation to the embodiments, the following Notes are furtherdisclosed.

Note 1. A first wireless communications system configured to share apredetermined bandwidth with another wireless communications system, thefirst wireless communications system comprising: a base station; and

a plurality of terminals connected to the base station. Each terminal ofthe plurality of terminals starts a process of detecting a wirelesssignal of the predetermined bandwidth, at a predetermined timing commonamong the plurality of terminals. The each terminal of the plurality ofterminals starts wireless signal transmission, using among bandwidthsincluded in the predetermined bandwidth, a same bandwidth or a mutuallydifferent bandwidth at a timing when a state in which no wireless signalof the predetermined bandwidth is detected by the process has continuedfor a predetermined period that is common among the plurality ofterminals.

Note 2. The wireless communications system according to Note 1, wherethe each terminal of the plurality of terminals calculates thepredetermined timing based on a timing at which the each terminalreceived a wireless signal from the base station and informationindicating a propagation delay between the each terminal and the basestation, and starts the process at the calculated predetermined timing.

Note 3. The wireless communications system according to Note 1 or 2,where the each terminal of the plurality of terminals, when the state inwhich no wireless signal of the predetermined bandwidth is detected bythe process has continued for the predetermined period, transmits a datasignal to the base station so as to be received at a reception timing ofthe base station in the predetermined bandwidth, the each terminaltransmitting the data signal based on information indicating apropagation delay between the each terminal and the base station. Theeach terminal of the plurality of terminals transmits a dummy signal ora preamble from the timing when the state in which no wireless signal ofthe predetermined bandwidth is detected by the process has continued forthe predetermined period, the each terminal transmitting the dummysignal or the preamble until the data signal is transmitted.

Note 4. The wireless communications system according to one of Notes 1to 3, where the base station transmits to the plurality of terminals, aparameter for calculating the predetermined timing. The each terminal ofthe plurality of terminals starts the process at the predeterminedtiming calculated based on a predetermined reference timing and theparameter transmitted from the base station.

Note 5. The wireless communications system according to Note 4, wherethe base station transmits to the plurality of terminals, the parameterthat is determined based on a random number.

Note 6. The wireless communications system according to one of Notes 1to 3, where the each terminal of the plurality of terminals calculatesthe predetermined timing based on information shared among the pluralityof terminals, and starts the process at the calculated predeterminedtiming.

Note 7. The wireless communications system according to Note 6, wherethe information shared among the plurality of terminals includesidentification information of a cell of the base station.

Note 8. The wireless communications system according to Note 6 or 7,where the information shared among the plurality of terminals includesidentification information of a subframe for performing the process.

Note 9. The wireless communications system according to one of Notes 1to 8, where the process of detecting a wireless signal of thepredetermined bandwidth is a process of detecting a wireless signal in abandwidth that among the bandwidths of the predetermined bandwidth, theeach terminal uses in the wireless signal transmission.

Note 10. The wireless communications system according to one of Notes 1to 9, where the process of detecting a wireless signal of thepredetermined bandwidth is a process of detecting a wireless signal inthe predetermined bandwidth entirely.

Note 11. A base station of a wireless communications system configuredto share a predetermined bandwidth with another wireless communicationssystem, the base station comprising: a control unit configured totransmit to a plurality of terminals connected to the base station, aparameter for calculating a predetermined timing that is common amongthe plurality of terminals, the control unit thereby causing eachterminal of the plurality of terminals to execute a process of startinga process of detecting a wireless signal of the predetermined bandwidthat the predetermined timing and starting wireless signal transmissionusing among bandwidths included in the predetermined bandwidth, a samebandwidth or a mutually different bandwidth at a timing when a state inwhich no wireless signal of the predetermined bandwidth is detected bythe process of detecting has continued for a predetermined period thatis common among the plurality of terminals; and a receiving unitconfigured to receive wireless signals transmitted from the plurality ofterminals.

Note 12. A terminal of a wireless communications system configured toshare a predetermined bandwidth with a second wireless communicationssystem, the terminal comprising: a detecting unit configured to start ata predetermined timing common to a second terminal connected to a basestation to which the terminal is connected, a process of detecting awireless signal of the predetermined bandwidth; and a transmitting unitconfigured to start wireless signal transmission using a bandwidthincluded in the predetermined bandwidth, the transmitting unit startingthe wireless signal transmission at a timing when a state in which nowireless signal of the predetermined bandwidth is detected by thedetecting unit has continued for a predetermined period that is commonto the second terminal.

Note 13. A processing method of a base station of a wirelesscommunications system configured to share a predetermined bandwidth withanother wireless communications system, the processing methodcomprising: transmitting, by the base station to a plurality ofterminals connected to the base station, a parameter for calculating apredetermined timing that is common among the plurality of terminals,the base station thereby causing each terminal of the plurality ofterminals to execute a process of starting a process of detecting awireless signal of the predetermined bandwidth at the predeterminedtiming and starting wireless signal transmission using among bandwidthsincluded in the predetermined bandwidth, a same bandwidth or a mutuallydifferent bandwidth at a timing when a state in which no wireless signalof the predetermined bandwidth is detected by the process of detectinghas continued for a predetermined period that is common among theplurality of terminals; and receiving, by the base station, wirelesssignals transmitted from the plurality of terminals.

Note 14. A processing method of a terminal of a wireless communicationssystem configured to share a predetermined bandwidth with anotherwireless communications system, the processing method comprising:starting, by the terminal, a process of detecting a wireless signal ofthe predetermined bandwidth, at a predetermined timing common to asecond terminal connected to a base station to which the terminal isconnected; and starting, by the terminal, wireless signal transmissionusing a bandwidth included in the predetermined bandwidth, the terminalstarting the wireless signal transmission at a timing when a state inwhich no wireless signal of the predetermined bandwidth is detected bythe process of detecting has continued for a predetermined period thatis common to the second terminal.

What is claimed is:
 1. A wireless communications system configured touse a predetermined bandwidth of an unlicensed bandwidth, the wirelesscommunications system comprising: a base station configured to transmita control signal that includes information indicating an offset timefrom a reference timing; and one or more terminals connected to the basestation, wherein the one or more terminals are configured to: calculatea transmission start timing, which is a timing at which the one or moreterminals are to start transmitting wireless signals, according to theoffset time indicated in the control signal that is received from thebase station; perform a process of detecting a wireless signal of thepredetermined bandwidth in a standard period before the transmissionstart timing, and when no wireless signal of the predetermined bandwidthis detected in the standard period, the one or more terminals starttransmission from the calculated transmission start timing using aportion less than all of the predetermined bandwidth.
 2. The wirelesscommunications system according to claim 1, wherein the control signalis transmitted from the base station using a PDCCH.
 3. The wirelesscommunications system according to claim 1, wherein the one or moreterminals calculate the transmission start timing using the controlsignal and a timing advance notified by the base station.
 4. Thewireless communications system according to claim 1, wherein the one ormore terminals start the process at a timing that is based on a timingat which a wireless signal from the base station is received andinformation indicating a propagation delay between the one or moreterminals and the base station.
 5. The wireless communications systemaccording to claim 1, wherein the one or more terminals transmit a dummysignal or a preamble from the transmission start timing until a datatransmission start timing.
 6. The wireless communications systemaccording to claim 5, wherein the one or more terminals, when the statein which no wireless signal of the predetermined bandwidth is detectedby the process has elapsed for a predetermined period, transmit a datasignal to the base station so as to be received at a reception timing ofthe base station in the predetermined bandwidth, the one or moreterminals transmitting the data signal based on information indicatingthe propagation delay between the one or more terminals and the basestation, and the one or more terminals transmit the dummy signal or thepreamble from a timing at which the state in which no wireless signal ofthe predetermined bandwidth is detected has elapsed for thepredetermined period, until the data signal is transmitted.
 7. Thewireless communications system according to claim 1, wherein the basestation determines based on a random number, a parameter for calculatinga timing of starting the process performed by the one or more terminals,and transmits the parameter to the one or more terminals.
 8. Thewireless communications system according to claim 1, wherein the one ormore terminals calculate a predetermined timing based on informationshared among the one or more terminals, and start the process at thecalculated predetermined timing.
 9. The wireless communications systemaccording to claim 1, wherein the process of detecting a wireless signalof the predetermined bandwidth is a process of detecting a wirelesssignal in the entire predetermined bandwidth.
 10. The wirelesscommunications system according to claim 1, wherein the control signalis transmitted from the base station using an RRC.
 11. A base station ofa wireless communications system configured to use a predeterminedbandwidth of an unlicensed bandwidth, the base station comprising: amemory; and a processor connected to the memory, the processorconfigured to: transmit to a terminal connected to the base station, acontrol signal that includes information indicating an offset time froma reference timing; and receive a wireless signal transmitted undercontrol so that transmission starts at a transmission start timingcalculated by the terminal according to the offset time indicated in thecontrol signal, wherein the terminal performs a process of detecting awireless signal of the predetermined bandwidth in a standard periodbefore the transmission start timing, and when no wireless signal of thepredetermined bandwidth is detected in the standard period, the terminalstarts transmission from the calculated transmission timing using aportion less than all of the predetermined bandwidth.
 12. A terminal ofa wireless communications system configured to share a predeterminedbandwidth of an unlicensed bandwidth, the terminal comprising: a memory;and a processor connected to the memory, the processor configured to:calculate a transmission start timing, which is a timing at which theterminal is to start transmitting wireless signals, according to anoffset time indicated in a control signal that is received from a basestation connected to the terminal; detect a wireless signal of thepredetermined bandwidth in a standard period before the transmissionstart timing; and perform control so that wireless signal transmissionstarts at the calculated transmission start timing using a portion lessthan all of the predetermined bandwidth, when no wireless signal of thepredetermined bandwidth is detected in the standard period.
 13. Aprocessing method of a base station of a wireless communications systemconfigured to share a predetermined bandwidth of an unlicensedbandwidth, the processing method comprising: transmitting, by the basestation to a terminal connected to the base station, a control signalthat includes information indicating an offset time from a referencetiming; and receiving, by the base station, a signal transmitted undercontrol so that transmission starts at a transmission start timingcalculated by the terminal according to the offset time indicated in thecontrol signal information, wherein the terminal performs a process ofdetecting a wireless signal of the predetermined bandwidth in a standardperiod before the transmission start timing, and transmits the wirelesssignal when no wireless signal is detected in the standard period usinga portion less than all of the predetermined bandwidth.
 14. A processingmethod of a terminal of a wireless communications system configured toshare a predetermined bandwidth of an unlicensed bandwidth, theprocessing method comprising: calculating, by the terminal, atransmission start timing, which is a timing at which the terminal is tostart transmitting wireless signals, according to an offset timeindicated in a control signal that is received from a base station;detecting, by the terminal, a wireless signal of the predeterminedbandwidth in a standard period before the transmission start timing; andperforming control so that wireless signal transmission starts at thecalculated transmission start timing using a portion less than all ofthe predetermined bandwidth when no wireless signal of the predeterminedbandwidth is detected in the standard period.